The present invention relates to paperboard laminates, and more particularly to a non-foil paperboard laminate useful for making containers for products such as fruit or citrus juices, beverages and the like as well as non-liquid dry products, wherein the laminate has good oxygen barrier characteristics as well as the ability to protect the products packaged therein against the loss of essential oils, flavor and Vitamins. Paperboard coated with low density polyethylene has been used for this purpose, but it falls short of providing an acceptable container, therefore additional barrier materials are required to achieve the desired goal. It is well known that impermeable materials such as aluminum foil, polar materials such as polyamides, polyethylene terephthalates, polyvinylidene chlorides, polyvinyl chlorides, etc., and highly crystalline non-polar materials such as high density polyethylene and polypropylene provide good gas barrier characteristics and varying degrees of barrier to the absorption and/or transmission of non-polar citrus juice flavor oils such as d-Limonene et al. However, when additional barrier materials are added to such structures, the manufacturing process becomes complex because of the basic incompatibility of some added materials with paperboard and low density polyethylene. Nevertheless, polyethylene is the most desirable material to have on both the inner and outer surfaces of such a laminate in order to achieve reliable and easy heat sealability when containers are formed.
U.S. Pat. Nos. 4,789,575 and 4,802,943 disclose a product and process for the manufacture of a laminate structure having inner and outer layers of polyethylene including an additional barrier material, but the method for making the laminate requires more complex manufacturing steps than the present invention and achieves a structure having less reliability in the field. U.S. Pat. No. 4,513,036 discloses another structure having inner and outer layers of polyethylene, but the polypropylene barrier material does not provide very good performance against the loss of essential oils and Vitamin C. Other prior art related to the present invention is described in U.S. Pat. No. 4,289,830 which discloses a multi-layer, coextruded film incorporating a barrier structure substantially as used in the present invention; a reprint from PLASTICS WORLD, July 1984 entitled "Barrier plastics challenge foil", which discloses a barrier structure applied to paper substantially as used in the present invention; and, a publication of TAPPI PRESS entitled "High Barrier Polymers", presented at the 1986 TAPPI Coextrusion Seminar, Marriott Hilton Head, Hilton Head, SC, April 1-3 1986, which also shows a typical barrier structure as disclosed herein in the form of a film. Nevertheless, the invention disclosed and claimed herein is deemed to be unobvious over the teachings of this prior art.